//调用入口：

         public static int[][] StrassenMulti(int a [][], int b[][]){int acow = a.length, acol = a[0].length, bcow = b.length, bcol = b[0].length;if(acow!=acol || bcow != bcol || acow != bcow) return MatrixMulti(a,b);if((acow &(acow -1 )) != 0) return MatrixMulti(a,b);//不是2的幂//只有符合2的幂才满足Strassen算法使用条件if(acow == 2) return MatrixMulti(a,b);else {int[][] A11 = new int[acow/2][acow/2];int[][] A12 = new int[acow/2][acow/2];int[][] A21 = new int[acow/2][acow/2];int[][] A22 = new int[acow/2][acow/2];nnMatrixSplitTo4Block(a,A11,A12,A21,A22);int[][] B11 = new int[acow/2][acow/2];int[][] B12 = new int[acow/2][acow/2];int[][] B21 = new int[acow/2][acow/2];int[][] B22 = new int[acow/2][acow/2];nnMatrixSplitTo4Block(b,B11,B12,B21,B22);int [][]S1 = MatrixNeg(B12 ,B22);int [][]S2 = MatrixPlus(A11 , A12);int [][]S3 = MatrixPlus(A21 , A22);int [][]S4 = MatrixNeg(B21 , B11);int [][]S5 = MatrixPlus(A11 , A22);int [][]S6 = MatrixPlus(B11 ,B22);int [][]S7 = MatrixNeg(A12 , A22);int [][]S8 = MatrixPlus(B21 , B22);int [][]S9 = MatrixNeg(A11 , A21);int [][]S10 = MatrixPlus(B11 , B12);int [][]P1 = StrassenMulti(A11 , S1);int [][]P2 = StrassenMulti(S2 , B22);int [][]P3 = StrassenMulti(S3 , B11);int [][]P4 = StrassenMulti(A22 , S4);int [][]P5 = StrassenMulti(S5 ,S6);int [][]P6 = StrassenMulti(S7 , S8);int [][]P7 = StrassenMulti( S9 , S10);int [][]C11 = MatrixPlus(MatrixNeg(MatrixPlus(P5, P4), P2) , P6);int [][]C12 = MatrixPlus(P1 , P2);int [][]C21 = MatrixPlus(P3,  P4);int [][]C22 = MatrixNeg(MatrixNeg(MatrixPlus(P5 , P1) , P3) , P7);return MatrixBlockPlus(C11,C12,C21,C22);}}

//将矩阵分为四个子矩阵public static void nnMatrixSplitTo4Block(int [][]src, int [][]A11, int [][]A12, int [][]A21, int [][]A22){int n = src.length;for(int i = 0; i<A11.length+A21.length; i++)for(int j = 0; j<A11[0].length+A12[0].length; j++){if(i<A11.length){if(j<A11[0].length){A11[i][j] = src[i][j];}else{A12[i][j-A11[0].length] = src[i][j];}}else{if(j<A21[0].length){A21[i-A11.length][j] = src[i][j];}else{A22[i-A11.length][j-A12[0].length] = src[i][j];}} }}

//将四个矩阵合并为一个矩阵public static int[][] MatrixBlockPlus(int [][]A11, int [][]A12, int [][]A21, int [][]A22){if(A11[0].length+A12[0].length != A21[0].length+A22[0].length || A11.length+A21.length != A12.length+A22.length) return null;int result[][] = new int[A11.length+A21.length][A11[0].length+A12[0].length];for(int i = 0; i<A11.length+A21.length; i++)for(int j = 0; j<A11[0].length+A12[0].length; j++){if(i<A11.length){if(j<A11[0].length){result[i][j] = A11[i][j];}else{result[i][j] = A12[i][j-A11[0].length];}}else{if(j<A12[0].length){result[i][j] = A21[i-A11.length][j];}else{result[i][j] = A22[i-A11.length][j-A12[0].length];}} }return result;}

//矩阵减法public static int[][] MatrixNeg(int a[][], int b[][]){int temp[][] = new int[b.length][b[0].length];for(int i = 0 ;i<b.length; i++){for(int j = 0; j <  b[0].length; j++){temp[i][j] = (-1) * b[i][j];}}return MatrixPlus(a,temp);}

//矩阵加法public static int[][] MatrixPlus(int a[][], int b[][]){if(a[0].length  != b[0].length || a.length != b.length) return null;int result[][] = new int[a.length][a[0].length];for(int i = 0; i<a.length; i++)for(int j = 0; j<b.length; j++){result[i][j] = a[i][j]+ b[i][j];}return result;}

//矩阵乘法public static int[][] MatrixMulti(int a[][], int b[][]){//     a的列数不等于 b行数                      //列数int cow = a.length;//结果的行数int col = b[0].length;//结果的列数if(a[0].length  != b.length ) return null;else{int result[][] = new int[a.length][b[0].length];for(int i = 0; i<cow; i++)for(int j = 0; j<col; j++){for(int k = 0; k<a[0].length; k++){result[i][j] +=a[i][k] * b[k][j]; }}return result;}}